Showing papers in "Renewable & Sustainable Energy Reviews in 1999"

A review of progress in thermophotovoltaic generation of electricity

Abstract: The author begins with an Introduction in which he discusses basic concepts, recent developments, potential advantages offered by TPV systems and a historical background. He then provides a background in blackbody radiators and examines selective and rare-earth oxide radiators. He discusses modelling, fabrication and characterization of TPV convertors, particularly those based on GaSb and InGaAs. He examines the several approaches to recirculating the sub-bandgap photons and ends with a section on modelling of TPV system performance, and conceptual designs and demonstration of TPV systems, including solar powered, biofueled nuclear-fueled, liquid hydrocarbon-fueled, diesel-fueled, propane fueled, and natural gas fueled TPV systems.

Recent directions of world hydrogen production

Abstract: Hydrogen can be produced on a large scale through economically favorable raw materials and processes. Utilization of water as an exhaustible supply of hydrogen is well known. This is very much an area open to research, so that traditional methods can be considered, as well as non-traditional approaches. This paper examines the present status and looks at different approaches for technological advances. The paper reports on some of the new developments in the progress of the recent directions of world hydrogen production, with emphasis on photolytical hydrogen processes. The aim of this article is to inform the reader of new research on hydrogen production.

Drying technologies for an integrated gasification bio-energy plant

Abstract: Forced drying of the biomass feedstock is nearly always necessary in an Integrated Gasification Bio-energy Plant (IGBP), and a dryer can represent the highest capital cost item in the pre-treatment section of such a plant. Despite this, there has been relatively little attention paid to the selection and performance of such processes. This review first considers the general requirement for feedstock drying in an IGBP. Brief discussion follows of the theory of evaporative drying, and of the classification of dryer types. The characteristics of biomass feedstocks and IGBP’s of relevance to the drying process are then discussed. Suitable dryer types for an IGBP are then identified and described in detail, with performance data for the drying of biomass feedbacks provided where available.

Porous silicon in solar cell structures : a review of achievements and modern directions of further use

Abstract: Porous silicon, which is being obtained by electrochemical etching of silicon wafers in electrolytes on the base of hydrofluoric acid, recently attracted the attention of specialists in photovoltaics even more due to a number of its unique properties. However, at present, acceptable results are obtained for the use of porous silicon as antireflecting coating for silicon solar cells only. In the present paper, previous experience of the use of por-Si in the silicon solar cells has been reviewed. On the base of examination of the porous silicon properties, a number of new directions of improvement of photoconversion efficiency of structures with optimized layers of porous silicon are proposed. The results of numerical calculations carried confirm perspectiveness of use of porous silicon for efficiency improvement for different types of silicon solar cells. These can be increased of their internal quantum efficiency, expansions of operating spectral range toward ultra-violet and infrared spectrum range, decrease of losses of photogenerated power due to the influence of bulk and surface recombination.

Sukatani revisited: on the performance of nine-year-old solar home systems and street lighting systems in Indonesia

Abstract: In 1988, 86 solar home systems, SHS, and 15 street lighting systems, SLS, were installed in the village of Sukatani in the province of West Java of Indonesia. The systems have a PV array of 80 Wp. In this paper we analyse the performance of these systems. For this purpose we use monitoring data and data from field surveys recorded in the period 1988–1993 and data collected in a field survey in 1997. This survey comprised both technical measurements on 62 solar home systems and interviews with 22 users of these systems. We found that, although the failure rate of street lighting systems is high, the villagers have a positive opinion about these systems. Further, we found that technically the solar home systems performed well. The users are satisfied about the performance. However, in the course of time the configuration of the SHS has changed: villagers have replaced most of the strip lights with cheap home-made candescent lamps and have replaced the initially-installed 100 Ah capacity solar batteries with cheaper locally produced 70 Ah capacity car batteries. From an analysis of monitoring data we found that the average irradiation in Sukatani is 4.2 kW/m2/day, which is a common value for Indonesia, but more than expected in 1988 when the systems were installed (3.5 kWh/m2/day). Furthermore, we found that daily electricity consumption per SHS can be as high as 25 Ah/day. Average values, however, range from 8.8 to 14.8 Ah/day, which is 15–50% below the daily load used in the design calculations (17.4 Ah/day). However, the average daily electricity consumption is close to the recommended value on the instruction sheets given to the users of the SHS. Because of the low demand of electricity the average performance ratio is 49%. By means of an energy loss analysis of the PV systems we found that 15% of the theoretically available energy from the array cannot be fed in the battery because it is fully charged. The replacement of 100 Ah batteries by 70 Ah batteries was justified on the grounds of the low electricity consumption of the SHS users in the period 1988–1993. On the basis of field surveys we found that the average lifetime of the 100 Ah and 70 Ah batteries is 4 and 3.5 years, respectively. The realized battery lifetime is rather long compared with other SHS projects in the world. While the average battery size in Sukatani decreased in course of time, we found on the basis of interviews with users of SHS that the average daily electricity consumption increased. We found a value of 18 Ah/day in 1997. Furthermore, the spread in the demand of electricity in 1997 and the use of other than initially-installed appliances, such as small incandesent bulbs and intercoms, indicates the need for a broad offer of system sizes and low power appliances. By means of design calculations we found that PV arrays in the range of 35–130 Wp are needed to satisfy different demand patterns. We conclude that monitoring by means of data loggers is a useful approach to allow the analysis of the long-term system performance. To increase the statistical reliability of results, monitoring should be supplemented by field measurements and interviews with users. However, due to the deviation between real and narrated experiences, interviews alone may not be sufficient to assess an SHS project.

Solar thermal water pumping systems: a review

Abstract: A number of attempts have been made by scientists to utilize solar energy for irrigation water pumping. It is mainly a problem of conversion of heat energy available from the sun, to mechanical energy. Some ingenious methods have been devised to utilize the available energy at low temperatures. This paper reviews past efforts to develop solar thermal water pumping systems which employ either conventional pumps or unconventional pumps, and emphasizes how the system modifications were made to suit different pumping conditions and requirements.

Renewable energy in Russia: markets, development and technology transfer

Abstract: Five potential markets in Russia offer commercial opportunities for renewable energy that are nearly cost-competitive with conventional forms of energy—grid-connected electricity from wind power, electricity for villages and small settlements from hybrid wind-diesel and biomass, district heating for buildings from biomass, hot water for buildings from solar thermal, and electricity and heat from geothermal. Over the last several decades the Soviet Union conducted research and development on several forms of renewable energy. Technological infrastructure, scientific and technical knowledge, engineering and technical skills, and factories and equipment are all well developed assets. But the translation of these assets into commercial renewable energy technologies and markets is a problem because associated market-oriented skills and institutions are still lacking. Many barriers also exist, including lack of information and demonstration experience, lack of long-term commercial financing, a perceived climate of high investment risk, technology acceptance, some direct and indirect energy price subsidies (most energy prices have risen to “market” levels), utility monopolies and the absence of operational regulatory frameworks for independent power producers, and historical enterprise specialization. Market intermediation is very important for renewable-energy investments and technology transfer, providing the knowledge, information, skills, services, financing, and analysis that is necessary to overcome barriers. Joint ventures with foreign multinational corporations represent another important means for overcoming barriers, one that takes advantage of Russian technological capabilities. Four case studies illustrate the most prominent examples of renewable energy technology transfer with Russia, Ukraine, and the Baltic States during the period 1992–1996.

Fuel cell cogeneration system : a case of technoeconomic analysis

Abstract: UNESP, Sao Paulo State Univ, Coll Engn Guaratingueta, Dept Energy, BR-12500000 Guaratingueta, SP, Brazil